Malaria is a major infectious disease. Conservative estimates predict 2-300 million people are afflicted and over a million children die from the infection each year. The growing treat of drug resistant forms of malaria has created an urgent requirement for new drugs. Targeting unique features of the parasite not found in host cells provides one approach to new drug development. Plasmodium falciparum causes the most virulent form of human malaria. A striking feature of P. falciparum erythrocyte infection is targeting parasite proteins to the red cell. These targeting events must be mediated by signals on the proteins. However, unlike organelles of yeast and mammalian cells, destinations in the red cells lie beyond the plasma membrane of the parasite. Moreover, the red cell has no endogenous transport structures or machinery. Thus signals that require targeting proteins to the vacuolar and intra-erythrocytic milieu must be unique. The long term aim of this proposal is to identify and characterize these signals and the mechanisms by which they function in novel secretory signaling pathways in a lower eukaryote. The studies will contribute to our understanding of the basic biology of the parasite as well as open up new targets for therapy, and thereby contribute to human health. Molecular genetic tools using transfection combined with high resolution imaging techniques and biochemical subcellular fractionation assays will be used to express secretory constructs as trans genes and evaluate the functions of putative targeting signals in infected cells. The consequence of trans gene expression on essential, cellular processes such as hemozoin (the black pigment of malaria formation and resistance to existing anti-malarials will be evaluated in parasites grown in vitro culture. These studies may be important for understanding existing mechanisms of malarial drug resistance.